Could something be blocking this slide from closing. Putting it in a bind so it takes more pressure to close it and could that something be the cylinder itself. If the piston too tight because it's too large or the cylinder warped. If you can get to it, measure the cylinder OD in several places around it to see if its round. You will need a pair of calibers if you don't have them ask your friends. Someone should be able to come up with them. The cylinders are thin wall and it would be easy to damage one in assembly or even before.
Lynwood

Could something be blocking this slide from closing. Putting it in a bind so it takes more pressure to close it and could that something be the cylinder itself. If the piston too tight because it's too large or the cylinder warped. If you can get to it, measure the cylinder OD in several places around it to see if its round. You will need a pair of calibers if you don't have them ask your friends. Someone should be able to come up with them. The cylinders are thin wall and it would be easy to damage one in assembly or even before.
Lynwood

I don't think it's on a bind or block because I can let it set like over night and then try to close it and it might close just fine. or I reverse hydraulic lines on the valve block which is under the Lippert control panel and it will close.
I have a couple of friends that are maintenance in the coal mines around here and they work with hydraulic jacks all the time. they said it sounds like a check valve not opening happens often under ground just on a larger scale.

I don't think it's on a bind or block because I can let it set like over night and then try to close it and it might close just fine. or I reverse hydraulic lines on the valve block which is under the Lippert control panel and it will close.
I have a couple of friends that are maintenance in the coal mines around here and they work with hydraulic jacks all the time. they said it sounds like a check valve not opening happens often under ground just on a larger scale.

Friend of mine fixed similar problem on a Montana next to him in a camp ground. Bear in mind this friend can fix anything. He took the pump apart and found a piece of plastic in the fluid had hung up in the check valve. Observed the pump is a gear pump similar to oil pump in car engine.
He and I used to build drag race engines.